Author ORCID Identifier
https://orcid.org/0009-0006-8607-7720
Date of Award
8-27-2026
Document Type
Thesis (Ph.D.)
Department or Program
Ecology, Evolution, Environment and Society
First Advisor
Caitlin E. Hicks Pries
Second Advisor
Matthew P. Ayres
Third Advisor
Ross A. Virginia
Abstract
Permafrost soils store more than 30% of global soil carbon, yet current Earth system models poorly represent the mineralogical, geochemical, and biological processes that govern its persistence and vulnerability to thaw. This dissertation addresses this gap through three studies conducted across a landscape age and geochemical gradient on Alaska's North Slope, examining the mechanisms that stabilize and destabilize organic and inorganic carbon pools in Arctic soils. The first chapter shows that organo-mineral associations vary systematically with landscape age, parent material, and soil depth. Interactions between soil organic carbon and reactive aluminum- and iron-bearing mineral phases were strongest in acidic soils, and a robust relationship between calcium and organic carbon at these sites suggests calcium-mediated protection is more widespread than previously recognized. Differences between active-layer and permafrost soils further indicate that depth defines distinct mineralogical and chemical environments with differing capacities for carbon protection. The second chapter identifies siderite (FeCO₃) as a previously underrecognized pool of inorganic carbon in Arctic permafrost. Siderite was detected across multiple geochemical settings but was absent from seasonally thawed active-layer soils, suggesting that frozen soils harbor an inorganic carbon reservoir that may be sensitive to thaw-driven mineral transformation. This finding broadens the conventional, organic-carbon-centered view of the permafrost carbon pool. The third chapter demonstrates that fresh carbon inputs, simulated through artificial root exudate additions, stimulate microbial respiration and prime the decomposition of native soil carbon, with stronger effects in permafrost than in the active layer. The magnitude of this priming effect was related to soil pH and the abundance of non-crystalline mineral phases, linking plant-derived carbon inputs to both microbial and geochemical controls on carbon vulnerability. Together, these findings show that permafrost carbon vulnerability cannot be predicted from bulk carbon quantity alone: persistence depends on where carbon is stored, the minerals with which it associates, the surrounding chemical conditions, and the biological processes that access it. By integrating mineralogical, geochemical, and biological perspectives, this dissertation provides a more mechanistic framework for anticipating how Arctic soils will respond to continued warming, with implications for improving representations of the permafrost carbon–climate feedback in Earth system models.
Recommended Citation
Montaño López, Fernando de Jesús, "Carbon on Thin Ice: Mechanisms of Carbon Persistence in Arctic Soils" (2026). Dartmouth College Ph.D Dissertations. 557.
https://digitalcommons.dartmouth.edu/dissertations/557
